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Patient skin dose measurements during coronary interventional procedures using Gafchromic film

This article has been downloaded from IOPscience. Please scroll down to see the full text article. 2010 J. Radiol. Prot. 30 585 (http://iopscience.iop.org/0952-4746/30/3/012) View the table of contents for this issue, or go to the journal homepage for more

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IOP PUBLISHING

JOURNAL OF RADIOLOGICAL PROTECTION

J. Radiol. Prot. 30 (2010) 585–596

doi:10.1088/0952-4746/30/3/012

Patient skin dose measurements during coronary interventional procedures using Gafchromic film C K Ying and S Kandaiya1 School of Physics, Universiti Sains Malaysia (USM), Penang, Malaysia E-mail: [email protected]

Received 21 January 2010, in final form 20 April 2010, accepted for publication 1 June 2010 Published 8 September 2010 Online at stacks.iop.org/JRP/30/585 Abstract Interventional cardiology (IC) procedures are known to give high radiation doses to patients and cardiologists as they involve long fluoroscopy times and several cine runs. Patients’ dose measurements were carried out at the cardiology department in a local hospital in Penang, Malaysia, using Gafchromic XR-RV2 films. The dosimetric properties of the Gafchromic film were first characterised. The film was energy and dose rate independent but dose dependent for the clinically used values. The film had reproducibility within ±3% when irradiated on three different days and hence the same XRRV2 dose–response calibration curve can be used to obtain patient entrance skin dose on different days. The increase in the response of the film post-irradiation was less than 4% over a period of 35 days. For patient dose measurements, the films were placed on the table underneath the patient for an under-couch tube position. This study included a total of 44 patients. Values of 35–2442 mGy for peak skin dose (PSD) and 10.9–344.4 Gy cm2 for dose–area product (DAP) were obtained. DAP was found to be a poor indicator of PSD for PTCA procedures but there was a better correlation ( R 2 = 0.7344) for CA + PTCA procedures. The highest PSD value in this study exceeded the threshold dose value of 2 Gy for early transient skin injury recommended by the Food and Drug Administration. (Some figures in this article are in colour only in the electronic version)

1. Introduction In coronary angiography (CA) a small tube called a catheter is threaded to the coronary arteries and then a contrast dye is injected to highlight the blood vessels and x-ray images are taken. The cardiologist has then the information regarding the number and location of blockages 1 Author to whom any correspondence should be addressed.

0952-4746/10/030585+12$30.00 © 2010 IOP Publishing Ltd

Printed in the UK

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as well as the severity of the blockages in a patient. The cardiologist can then proceed to percutaneous transluminal coronary angioplasty (PTCA), where a balloon catheter will open the narrow vessel and a stent is inserted to keep the vessel open. In all these procedures fluoroscopic imaging is prolonged and the number of acquired images is large. This can result in high radiation doses to the patient’s skin, which can then cause deterministic effects. Due to growing concern about high radiation dose in complex procedures, the Food and Drug Administration [1], the World Health Organization [2] and the International Commission on Radiological Protection [3] have published documents on how to avoid deterministic effect of skin injuries in cardiology procedures. Therefore, there is a need to assess patient skin dose routinely. Most interventional x-ray machines are equipped with dose–area product (DAP) meters. However, DAP is a poor indicator of skin dose and there is a poor correlation between DAP and skin dose [4–7]. Patient skin dosimetry using thermoluminescence dosimeters (TLDs) is inadequate since it is difficult to locate the position of maximum skin dose [8]. Slow radiographic film as well as Gafchromic film can be used to map skin dose distribution over a large area. Slow radiographic film such as Kodak X Omat V and EDR2 (extended dose range), which are used in radiotherapy, have been characterised to measure skin doses in cardiology procedures [9, 10]. Kodak EDR2 has a wider measurement dose range than Kodak X Omat film but it may reach saturation at doses greater than 500 mGy. In PTCA procedures doses may exceed 500 mGy. The recently introduced Gafchromic film [11], reflective type XR-type R (XR-R) and transmission type XR-type T (XR-T), have optimised sensitivity in the energy range of 50–200 kVp and can measure doses in the range of 1–15 Gy. These films undergo a colour change after irradiation and require no chemical processing, unlike Kodak films. However, Gafchromic films are more expensive than Kodak films. Currently, there is a lack of patient dose data during interventional cardiology procedures in Malaysia. The objective of this study was then to determine the peak skin doses (PSDs) for patients undergoing PTCA and CA + PTCA in a cardiac catheterisation laboratory at a local hospital. The measured values can be incorporated into the limited available data in Malaysia. The Gafchromic XR-RV2 film was chosen to map skin dose as higher doses were expected in these procedures. The dosimetric parameters of the Gafchromic film such as energy dependence, dose–response, dose rate dependence and reproducibility were first studied. The dose measurements from films were also compared with DAP to establish any correlation between DAP and the peak skin dose.

2. Material and methods 2.1. Gafchromic® XR-RV2 ISP (International Specialty Products, Wayne, NJ) have introduced a new reflective Gafchromic® film XR-RV2 to replace Gafchromic® XR-R. XR-RV2 film has a higher sensitive dose range (1 cGy–50 Gy) than XR-R film. Gafchromic® XR-RV2, shown in figure 1, has been developed to specifically measure absorbed dose at both low and high energy photons where the energies are between 30 keV and 30 MeV. The active layer of Gafchromic® XR-RV2 is approximately 17 µm. It is sandwiched between two sheets of polyester: one transparent film substrate with thickness 97 µm and one opaque, white film substrate with thickness 97 µm. The transparent polyester substrate used in the film contains a yellow dye. The yellow dye enhances the visual contrast of the chromatic changes when the film is exposed to radiation. The yellow dye also protects the active layer against exposure by UV and blue light and thereby enables the film to be even more tolerant

Patient skin dose measurements during coronary interventional procedures using Gafchromic film

587

Figure 1. Structure of Gafchromic® XR-R film [11].

of being handled in the light. The opacity of the white substrate in XR-RV2 is provided by a baryta filling. It employs the same active component as XR-R film but includes a proprietary high Z material, thus making it more sensitive than XR-R film. This thickness of layer may vary from one batch of films to another batch. Each batch of films comes with a specific lot number. Hence a new calibration should be done when a different batch is used [11]. Gafchromic XR-RV2 radiochromic dosimetry films are normally measured with reflective type film scanners [11–13]. When the active component in the film is exposed to radiation, it reacts to form a blue coloured polymer with an absorption maximum at about 635 nm [14]. Therefore, the response of Gafchromic XR-RV2 is enhanced by measurement with a red light.

2.2. Characterisation of Gafchromic® XR-RV2 film Parameters such as energy and dose dependence, reproducibility and post-exposure growth of Gafchromic XR-RV2 film were first studied to ensure the suitability of the film for in vivo skin dose measurements. Gafchromic XR-RV2 film was cut into 2 cm × 3 cm pieces and then irradiated with varying x-ray energies using the Philips Integris HM3000 interventional unit. A 1 cm3 flat ionisation chamber type 77337 (PTW, Freiburg) was used to measure the air kerma. According to the manufacturer’s guidelines, the ion chamber which was connected to the PTW UNIDOS electrometer has a total uncertainty of ±5%. Since the interventional unit was an under-couch system, the pre-cut films were positioned below a 30 cm × 30 cm and a 10 cm thick Perspex phantom to provide sufficient backscatter with the white side of the XR-RV2 film facing the entrance x-ray beam. The 10 cm Perspex represents the backscatter from the patient. Hence, in the interventional unit as well as in the Toshiba x-ray machine, the experiments were performed with 10 cm Perspex as backscatter material. Hence the backscatter conditions remain the same for both the machines. The phantom had a drilled groove, which served as a holder for the PTW 77337 ion chamber, which was positioned above the film facing the source (figure 2). The dose delivered to the film was read from the electrometer. To maximise the dose rate and to reduce the time of irradiation of films, the films were placed at two different distances: as close as possible to the source to detector distance (SDD) of 52 cm and at the exit window of the tube housing. Varying thicknesses of lead apron were placed on top of the set-up tool. The lead apron would increase the tube current (mA) and kVp while protecting the digital image intensifier from exposure saturation, so that the different dose rates and different energy kVps were delivered to the films. The XR-RV2 films were scanned 24 h after irradiation to acquire the response as a pixel value (PV).

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Figure 2. The setting of the Gafchromic film for the interventional unit x-ray beam, with the ionisation chamber positioned on top of the film in the centre area.

The net mean pixel value (NMPV) was calculated using equation (1): MPVunexp NMPV = k MPVexp

(1)

where MPVunexp is the mean pixel value obtained before radiation exposure, that is the film background, MPVexp is the mean pixel value obtained after radiation exposure and k is a constant term with a value of 10 000 [15]. This formula allows the ratio of MPVunexp /MPVexp to be unity for the unirradiated film and then the ratio increases with increasing dose. The NMPV was the parameter used to study the dependence of the XR-RV2 films on photon energy, dose and dose rate. 2.2.1. Energy and dose dependence. The air kerma was delivered to each film with different energy x-ray beams ranging from 54 to 125 kVp using the interventional unit. Different kVp values were achieved by using different thicknesses of lead. These values are representative of the typical kVp values used in the clinical interventional procedures. The half-value-layer (HVL) at 70 kVp is 3.1 mm Al whilst at 90 kVp the HVL is 3.8 mm Al. A series of known doses in the range of about 100 mGy to 2800 mGy were given using the experimental set-up shown in figure 2. 2.2.2. Reproducibility. The general irradiation method mentioned in section 2.2.1 was used. A Toshiba general x-ray machine was used to irradiate XR-RV2 films on three different days at energies ranging from 60 to 120 kVp. Here the HVLs fall within a range of 2.0–3.8 mm Al. The films were scanned 24 h after irradiation and the dose–response curve on three different days was plotted. 2.2.3. Post-exposure time dependence. Post-exposure pixel value growth is the response of the film in pixel values after irradiation. This was observed after 24 h of irradiation for two different dose values of 402 and 1058 mGy at 100 kVp x-ray energy. The mean pixel value was observed at different times for a period of 35 days. The films were kept in a light tight box in between readouts.

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Table 1. Patients’ demographic data.

Average Maximum Minimum

Weight (kg)

Age (years)

71.0 ± 14.0 100.0 49.0

60.0 ± 9.0 79.0 39.0

2.3. Scanning system According to the ISP [11], a flatbed colour scanner with 48 bit resolution or 16 bits/channel works best with Gafchromic films [12]. In this study, the irradiated XR-RV2 films were scanned in the reflective mode using an Epson V700 professional flatbed scanner and scanned in 48 bit RGB mode with a fluorescent lamp, in colour mode, at 72 dpi scanner resolution. Data extractions were done in the red channel as it had the maximum sensitivity to dose– response [12]. The film images were analysed with Image-J [16] using 16 bit images in TIFF format. 2.4. Patient dose measurements Patient dose measurements were carried out at the cardiology department at a local private hospital in Penang. The catheterisation laboratory in the cardiology department has a Philips Integris HM 3000 interventional unit (Philips Medical System, Best, The Netherlands) equipped with a DAP meter. The interventional unit was installed with a lead curtain below and a ceiling suspended screen. The lead curtains protect the cardiologists’ legs whilst the suspended screen protects the head from scattered radiation. The patient selection was random. This included 27 patients who underwent PTCA and 17 patients who underwent CA + PTCA. When the PTCA procedure proceeds immediately after the CA procedure it is named CA + PTCA. A series of data such as DAP value, fluoroscopy time, type of procedure, patient gender, weight and age was recorded for each procedure. The x-ray unit had passed quality control (QC) evaluation. During cardiology procedure, tube settings such as peak voltage and current were controlled by the automatic brightness control (ABC) but the couch position and entrance beam angle were changed manually. Pulsed fluoroscopy at 12.5 frames s−1 (12.5 f s−1 ) was used. 2.4.1. Patient selection. The patient demographic data are shown in table 1. Doses from 44 patients including 27 PTCA patients and 17 CA + PTCA patients were studied. 2.4.2. Film positioning. Gafchromic XR-RV2 (yellow side facing up) films were placed on the table underneath the patient for the under-table tube position and centred as close as possible to the most irradiated area of the patient. All the Gafchromic XR-RV2 films were scanned with the Epson V700 flat bed scanner and film images were analysed with Image-J [16]. The digitised images were analysed with 16 bit images in TIFF format. The peak skin dose was analysed through a film dose–response calibration curve. 3. Results and discussion 3.1. Characterisation of Gafchromic® XR-RV2 film 3.1.1. Energy and dose dependence. In clinical practice, the dose rates and x-ray energies of the interventional unit vary during PTCA procedures. It is then important to determine the

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Figure 3. Film dose–response curve obtained for XR-RV2 films irradiated at different x-ray energies.

Table 2. Response of XR-RV2 films irradiated at different x-ray energies. No

kVp

Dose (mGy)

MPV

NMPV

Std dev.

Std dev. in %

1 2a 3a 4 5 6 7 8 9 10

65 125 54 97 78 76 125 125 114 111

103 216 269 307 311 826 838 1590 1868 2777

41 860 33 838 34 828 30 851 34 791 26 363 26 295 19 364 18 197 15 376

11 262 12 976 12 608 14 233 13 550 17 882 17 928 24 345 25 907 30 661

113 115 122 113 118 119 112 111 120 119

0.3 0.4 0.4 0.4 0.4 0.5 0.4 0.6 0.7 0.8

a

Films placed at the exit window of the tube housing.

response of the XR-RV2 film irradiated under different x-ray energies and dose rates. The results obtained from XR-RV2 films irradiated at different x-ray energies are shown in table 2. The XR-RV2 films no. 2 and no. 3 were placed at the exit window of the tube housing, whilst the other films were placed at source to detector distance (SDD) of 52 cm. Therefore, different dose rates were delivered to the films at these two distances. The dose–response of the XR-RV2 films at different x-ray energies and different dose rates was plotted (figure 3) based on table 2. Figure 3 shows the film dose–response curve obtained from XR-RV2 films when irradiated at different energies from 54 to 125 kVp and dose range from 100–2800 mGy. As shown in figure 3, the dose–response of the XR-RV2 film in terms of NMPV at various energies fitted well to the polynomial line with R 2 value 0.9972 for different doses. For each net mean pixel value, the percentage error at the eight energies is within ±1%. The same dose at different kVps gave a similar response. Although the films were irradiated at different dose rates, the response of the film follows the same curve (figure 3). In conclusion, the response of the film is dose dependent but energy and dose rate independent. Thus the same calibration curve can be used to analyse peak skin doses for different patients where different beam qualities are used.

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Figure 4. Dose–response calibration curve performed on three different days.

Figure 5. The post-exposure time dependence: relative mean pixel value of the film response against time (days) is shown for two different dose values.

3.1.2. Reproducibility. The data from the XR-RV2 films irradiated and scanned on three different days was obtained and the dose–response was plotted and is shown in figure 4. The dose ranged from 40 to 1300 mGy. The dose–response is in terms of MPV, which is the mean pixel value of the irradiated film. Figure 4 shows that the dose–response calibration curve for the three different days can be fitted to a single quadratic line with a good regression coefficient of 0.9953. Therefore, the reproducibility of XR-RV2 film from the same batch was good and the same XR-RV2 dose– response calibration curve can be used to obtain patient peak skin dose in this study on different days. Here the film is not dependent on chemical processing. 3.1.3. Post-exposure time dependence. The film response in MPV against post-exposure time for two dose values of 402 and 1058 mGy is shown in figure 5. The MPV values were normalised to the MPV obtained 24 h post-exposure. The relative pixel value of the exposed film at two different doses is relatively constant within 35 postexposure days. The variation in film response was less than 3% for 402 mGy dose and less than 4% for 1058 mGy dose in the same period. In our study, all films were scanned one day after irradiation.

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Figure 6. XR-RV2 irradiated films from interventional procedures.

3.2. Patient dose measurements Patients’ data obtained in interventional cardiology procedures of PTCA and CA + PTCA are shown in table 3. The mean DAP value per procedure, the mean fluoroscopy and cine exposure time as well as the mean PSD are given in table 4. In the two procedures, the following values were obtained for the different parameters: cine frame, 285–3520; fluoroscopy time, 0.4–50.3 min; cinefluorography time, 0.38–4.69 min; DAP, 10.9–344.4 Gy cm2 ; PSD, 35– 2443 mGy (including backscatter); mean radiation field size at the entrance of the patient (denoted as average area in table 3), 53–139 cm2 . In PTCA procedures, the PSD of 19 patients had less than 1400 mGy, but two patients received more than 2000 mGy; the highest skin dose in the PTCA procedure was 2400 mGy. One contributing factor for the high PSD for patient 27 was the relatively long cine time (>4 min) compared to the other patients. However, for patient 16, the cardiologist had difficulty in threading the catheter in the heart artery and possibly the fluoroscopy and x-ray images were performed in close proximity at the same location. Patients receiving more than 2 Gy may be prone to early transient skin injury [1]. These patients should be monitored for skin injury and appropriate action should be taken if needed. In the CA + PTCA procedure, 14 patients had PSDs of less than 1000 mGy while three patients received PSD between 1000 and 1800 mGy. Both the mean PSD and DAP for CA + PTCA were less than those for PTCA procedures since some of the PTCA procedures were more complicated than the CA + PTCA procedures. The mean DAP value of this study was also compared with DAP values in the literature for PTCA procedures in recent years and is shown in table 5. The range of published DAP values is wide and the mean value of 122.2 Gy cm2 for PTCA procedure in this study is higher than those given in the reported studies. The European reference levels for CA and PTCA procedures are 45 Gy cm2 and 85 Gy cm2 respectively [23], whilst the guidance levels (75th percentile) from five countries are 50 Gy cm2 for CA and 125 Gy cm2 for PTCA of moderate complexity [24]. The DAP value of this study is within the guidance level of 125 Gy cm2 but exceeds the European reference level. The DAP values depend on the complexity of the procedure as well as on the skill and the experience of the cardiologists. It should be emphasised that, although DAP is an easily available measurement, the DAP measurement does not provide information regarding the most irradiated area in the patient’s skin, so the radiological risk cannot be deduced directly from this value. Therefore, the measurement for peak skin dose is needed. Examples of irradiated films from interventional procedures for patients 16, 27 and 38 are shown in figure 6. The region of peak skin dose is easily identified by the darkest patch. The overlapping fields are seen clearly on the films.

Patient skin dose measurements during coronary interventional procedures using Gafchromic film Table 3. (a) Dosimetric parameters for PTCA procedures. CA + PTCA procedures. No

593

(b) Dosimetric parameters for

No of Fluoroscopy Cine time images time (min) (min)

Total time (min)

DAP Average PSD (Gy cm2 ) (mGy) area (cm2 )

1230 498 1723 1193 naa 1117 2193 1228 398 416 750 379 841 780 285 511 493 2109 1448 476 512 771 1027 2161 551 1059 3520

28.4 8.9 12.3 11.4 13.9 11.7 41.2 27.6 2.9 8.7 9.3 8.2 9.2 22.3 22.9 29.0 4.3 34.8 8.9 6.4 6.4 12.7 15.0 29.0 8.3 47.1 39.9

1.64 0.66 2.30 1.59 na 1.49 2.92 1.64 0.53 0.55 1.00 0.51 1.12 1.04 0.38 0.68 0.66 2.81 1.93 0.63 0.68 1.03 1.37 2.88 0.73 1.41 4.69

30.04 9.56 14.60 12.99 na 13.19 44.12 29.24 3.43 9.25 10.30 8.71 10.32 23.34 23.28 29.68 4.96 37.61 10.83 7.03 7.08 13.73 16.37 31.88 9.03 48.51 44.59

205.7 54.4 122.8 86.1 na 101.1 289.1 173.2 19.5 71.8 95.0 40.0 101.4 139.0 64.5 135.1 20.8 210.7 88.4 52.2 35.3 76.0 109.0 223.5 54.6 273.7 334.4

1810 485 1135 954 1017 1958 1139 1303 193 673 523 381 1515 1230 864 2443 279 1611 718 681 804 640 1562 1638 227 737 2311

102 85 81 62 56 77 71 86 89 53 86 88 82 69 86 74 83 73 86 94 66 74 81 75 86 92 89

380 naa 1661 1456 894 509 753 1564 851 1166 3322 876 815 1387 798 1472 994

4.7 50.3 16.4 5.5 6.3 6.5 9.1 10.9 7.4 na 28.8 4.7 8.8 na 5.6 13.3 6.6

0.51 na 2.21 1.94 1.19 0.68 1.00 2.09 1.13 1.55 4.43 1.17 1.09 1.85 1.06 1.96 1.33

5.21 na 18.61 7.44 7.49 7.18 10.10 12.99 8.53 na 33.23 5.87 9.89 na 6.66 15.26 7.93

30.2 na 121.7 78.1 52.3 32.8 65.4 101.2 73.3 75.7 324.4 60.0 58.8 na 53.7 88.8 78.9

458 1046 1418 584 320 186 453 552 840 733 1732 296 279 537 344 553 670

90 83 90 86 88 55 90 74 86 70 75 91 67 74 90 79 94

(a) 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 (b) 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 a

No data were recorded.

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Figure 7. Correlation between DAP and PSD for PTCA and CA + PTCA procedures. Table 4. The mean DAP, mean time and mean PSD for the two procedures.

PTCA CA + PTCA a

Mean fluoroscopy time (min)

Mean cine time (min)

Mean total time (min)

Mean DAP (Gy cm2 )

Mean PSD (mGy)

17.8 ± 12.5 12.3 ± 12.2

1.42 ± 1.01 1.57 ± 0.91

19.37 ± 13.42a 11.17 ± 7.48

122.2 ± 86.1 86.4 ± 70.1

1068 ± 620 647 ± 415

One standard deviation. Table 5. Published PTCA values between 1995 and 2008. Authors

Year

Mean DAP (Gy cm2 )

Vano et al [17] Betsou et al [18] Padovani et al [19] Van de Putee et al [4] Tsapaki et al [20] Efstathopoulos et al [21] Morrish et al [22] This study

1995 1998 1998 2000 2003 2004 2008 2008/09

87.5 37.6 101.9 115.3 68.0 82.1 79.4 122.2 ± 86.1

The correlation between the DAP and PSD values for the two different procedures were studied and the results shown in figure 7. DAP had a poor correlation with the PSD for the PTCA procedures ( R 2 = 0.3517), the PTCA procedures were performed under long fluoroscopy times using many projections. A good correlation ( R 2 = 0.7344) was obtained between the PSD and DAP values for the CA + PTCA procedures. DAP can give a better indicator of peak skin dose in CA + PTCA procedures with short fluoroscopy times compared to PTCA procedures where fluoroscopy times were longer. Similar results were found when fluoroscopy times were plotted against PSD values for the two different procedures (figure 8). There was a reasonable correlation between the PSD and total fluoroscopy time ( R 2 = 0.7132) for the CA + PTCA procedures, while that for PTCA procedures on their own was poor ( R 2 = 0.2852). Time can give an indication of skin dose for short fluoroscopy times.

Patient skin dose measurements during coronary interventional procedures using Gafchromic film

595

Figure 8. Correlation between the PSD and total fluoroscopy time for PTCA and CA + PTCA procedures.

Poor correlation of PSD with DAP as well as fluoroscopy time has been reported in the literature for IC procedures [5, 7, 22, 24]. Here both slow films and Gafchromic films were used to measure PSD. 4. Conclusion The XR-RV2 radiochromic film is a good dosimetric film for interventional cardiology examination to map patient skin doses. The results obtained in this study show that XR-RV2 is suitable to monitor patient skin doses and for predicting possible skin injury when the threshold dose levels are exceeded. DAP is not an adequate indicator of patient skin dose. The wide variation in DAP values could arise from long fluoroscopy time, variation in cineangiography time, patient weight and anatomy, operator skill, the number of lesions and the field size used. DAP readings can be useful in assessing potential skin dose for fluoroscopy times less than 15 min; this only gives PSD of less than 1 Gy. Acknowledgments This study was partially supported by a USM-RU-PGRS research grant, the USM fellowship scheme and a USM short term research grant. The authors would like to thank all the cardiac laboratory staff and radiology staff involved in the study at the local hospital for their invaluable co-operation and assistance during the patients’ dose monitoring. References [1] FDA US Food & Drug Administration 1994 Avoidance of serious x-ray induced skin injuries to patient during fluoroscopically-guided procedures Med. Bull. 24 7–17 [2] WHO 1997 Joint WHO/ISH/CE Workshop on Efficacy and Radiation Safety in Interventional Radiology (MunichNeuherberg, Oct. 1995) (Germany: Bundesamt fur Starhlenschutz) BfS-ISH-178/97 [3] ICRP 2007 Recommendations of the International Commission on Radiological Protection ICRP Publication 103; Ann. ICRP 37 2–4

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[4] Van de Putte S, Verhaegen F, Taeymans Y and Thierens H 2000 Correlation of patient skin doses in cardiac interventional radiology with dose–area product Br. J. Radiol. 73 504–13 [5] Vano E, Gonzalez L, Ten J I, Fernandez J M, Guibelalde E and Macaya C 2001 Skin dose and dose–area product values for interventional cardiology procedures Br. J. Radiol. 74 48–55 [6] Morrell R E and Rogers A 2006 Kodak EDR2 film for patient skin dose assessment in cardiac catheterization procedures Br. J. Radiol. 79 603–7 [7] Delichas M G, Psarrakos K, Molyvda-Athanassopoulou E, Giannoglou G, Sioundas A, Hatziioannou K and Papanastassiou E 2005 The dependence of patient dose on factors relating to the technique and complexity of interventional procedures Phys. Medica 21 153–7 [8] Dogan B, Ol˘gar T, Toklu T, Ca˘glan A, Onal E and Padovani R 2009 Patient doses and dosimetric evaluations in interventional cardiology Med. Phys. 25 31–42 [9] Vano E, Guibelalde E, Fernandez J M, Gonzalez L and Ten J I 1997 Patient dosimetry in interventional radiology using slow film Br. J. Radiol. 70 195–200 [10] Guibelalde E, Vano E, Gonzalez L, Prieto C, Fernandez J M and Ten J I 2003 Practical aspects for the evaluation of skin doses in interventional cardiology using a new slow film Br. J. Radiol. 76 332–6 [11] Gafchromic radiochromic dosimetry film background information and characteristic performance data Online http://online1.ispcorp.com/ layouts/Gafchromic/index.html Accessed November 2008 [12] Alva H, Mercado-Uribe H, Rodriguez-Villafuerte M and Brandan M E 2002 The use of reflective scanner to study radiochromicfilm response Phys. Med. Biol. 47 2925–33 [13] Thomas G, Chu R Y L and Rabe E 2003 A study of GafChromic XR Type R film response with reflective-type densitometers and economical flatbed scanners J. Appl. Clin. Med. Phys. 4 307–14 [14] Cheung T, Butson M J and Yu P K N 2005 Reflection spectrometry analysis of irradiated Gafchromic XR type R radiochromic films Appl. Radiat. Isot. 63 127–9 [15] Rampado O, Garelli E, Deagostini S and Ropolo R 2006 Dose area product evaluation with Gafchromic XR-R films and a flat bed scanner Phys. Med. Biol. 51 403–9 [16] Rasband W S 1997-2009 Image J US National Institutes of Health, Bethesda, Maryland, USA http://rsb.info.nih. gov/ij/ accessed September 2008 [17] Vano E, Gonz´alez L, Fern´andez J M and Guibelalde E 1995 Patient doses in interventional radiology Br. J. Radiol. 68 1215–20 [18] Betsou S, Efstathopoulos E P, Katritsis D, Faulkner K and Panayiotakis G 1998 Patient radiation doses during cardiac catheterization procedures Br. J. Radiol. 71 634–9 [19] Padovani R, Novario R and Bernardi G 1998 Optimization in coronary angiography and percutaneous transluminal coronary angioplasty Radiat. Protect. Dosim. 80 303–6 [20] Tsapaki V, Kottou S, Vano E, Faulkner K, Giannouleas J, Padovani R, Kyrozi E, Koutelou M, Vardalaki E and Neofotistou V 2003 Patient dose values in a dedicated Greek cardiac centre Br. J. Radiol. 76 726–30 [21] Efstathopoulos E P, Karvouni E, Kottou S, Tzanalarridou E, Korovesis S, Giazitzoglou E and Katritsis D G 2004 Patient dosimetry during coronary interventions: a comprehensive analysis Am. Heart J. 147 468–75 [22] Morrish O W E and Goldstone K E 2008 An investigation into patient and staff doses from x-ray angiography during coronary interventional procedures Br. J. Radiol. 81 35–45 [23] Padovani R et al 2008 Reference levels at European level for cardiac interventional procedures Radiat. Protect. Dosim. 129 104–7 [24] Balter S, Miller D L, Vano E, Ortiz L P, Bernardi G, Cotelo E, Faulkner K, Nowotny R, Padovani R and Ramirez A 2008 A pilot study exploring the possibility of establishing guidance levels in x-ray directed interventional procedures Med. Phys. 35 673–80